**7. Selected Industrial Coating Types and Main Applications**

A large number of commercial coating solutions involving AlCr-based coatings are offered by PVD system manufacturers, job coating service centres and by tool and part manufacturers worldwide. The chemical compositions and the coating architectures vary, as do the deposition technologies and coating processes used. In the dominant arc source technology, the magnetic field set-up is particularly important as it influences the plasma conditions and coating properties. Within the group of sputtering technologies, a a great many more parameters can be varied, particularly in HiPIMS processes, e.g., pulse form and length.

The functionality of the coating-substrate system results from the quality and reproducibility of the whole process chain. Proper selection of the pre-treatment processing of the parts, for example, the cutting edges of cutting tools, is essential and must be carried out outside the coating chamber prior to deposition. Ion etching processing of the parts is performed to remove surface contamination and obtain sufficient coating adhesion. Process parameters are selected to manage stress in the coating. For commercial reasons, the process details are typically protected by the companies offering CrAl- and AlCr-based coatings.

It must be pointed out that a new challenge, that of sustainable surface engineering, e.g., the minimisation of energy consumption, the selection of the coating material, reducing waste, and facilitating recycling, is attracting increasing interest. A comprehensive overview of all types of commercial AlCr-based coatings is beyond the scope of this review. However, a brief introduction to the application field of AlCr-based coatings will be provided through a characterisation of three different coating types.

#### *7.1. Examples for Industrially Applied Coatings Types*

Within the authors' company, more than 10 variations of AlCr-based coatings have been or are in use (different coating thicknesses and other minor variations are not counted). As an example of the technology status, three coating types will be roughly characterised to highlight features of the deposition process and the coating property ranges. Selected coating properties are shown in Table 3. Two deposition methods are applied: arc and HiPIMS (S3p). The coatings have different alloying elements and various architectures.


**Table 3.** Brief characteristics of selected industrially applied AlCrN-based coating

 types.

The first coating type is a monolayer deposited by cathodic vacuum arc (e.g., BALINIT® ALCRONA PRO). The second coating type is a multilayer coating employing the layer sequence (AlCr)N/(TiSi)N (e.g., BALINIT® HELICA), also applied by arc deposition. The third coating type is a monolayer sputter coating deposited using an advanced HiPIMS process (S3p), which can also be employed for multilayers.

The coating morphologies are shown in the cross-sectional images obtained by SEM together with a ball crater. The fine columnar structure of the arc monolayer (AlCr)N is shown in Figure 26.

**Figure 26.** Cross-section and calotte of an industrially applied arc coating, BALINIT® ALCRONA PRO, courtesy of Oerlikon Balzers.

The fine-grained morphology of an arc multilayer (AlCr)N/(TiSi)N is demonstrated in Figure 27. This is a classical multilayer deposited by alternated switching on the sources with the different cathode materials. The added (TiSi)N sublayers increase the hardness of the coating.

**Figure 27.** Cross section and calotte of an industrially applied arc multilayer coating (AlCr)N/(TiSi)N, with top layer of (TiSi)N, BALINIT® HELICA, courtesy of Oerlikon Balzers.

The dense columnar structure with a low defect density and high smoothness of HiPIMS (AlCr)N monolayers is clearly seen in Figure 28. This coating is particularly advantageous for micro tools and other small parts that are sensitive to droplets in arcdeposited coatings.

**Figure 28.** Cross-section and calotte of an industrially applied HiPIMS (S3p) (AlCr)N coating, BALIQ® ALCRONOS, courtesy of Oerlikon Balzers.
